Leishmania parasites belong to the family Trypanosomatidae and cause potentially fatal cutaneous and visceral infections in 18 million infected humans worldwide. No protective vaccine currently exists and treatment involves use of toxic antimonial compounds. All trypanosomatids, which includes the human parasites Typanosoma in addition to Leishmania, possess a unique organelle called the glycosome. The glycosome is considered a member of the peroxisome family of microbody organelles. This organelle functions to compartmentalize the first glycolytic reactions, as well as other vital metabolic processes, and has been proposed as a target for anti-parasite chemotherapy. The specific aims of this proposal are to isolate glycosome deficient mutants of Leishmania, analyze the potential role of the glycosome in virulence, and isolate genes which are involved in glycosomal biogenesis. Mutagenesis followed by a forward genetic approach will be used to isolate Leishmania lacking glycosomes. Mutants deficient in glycosomes will be characterized physically and biochemically. The mutants will also serve as a starting point for the isolation and characterization of genes involved in glycosomal biogenesis. Complementation studies using a Leishmania cosmid library and selection against glycosome deficient mutants will allow for the cloning of genes involved in glycosome biogenesis. Genes cloned will be compared to known peroxisomal biogenesis genes. In addition to further elucidating the biological role of glycosome compartmentalization, the project is designed to determine the possible differences between glycosomes and peroxisomes that could be exploited in anti-parasite therapy, as well as answer basic questions about microbody organelle assembly.